During the first part, we explain how to set up a local WordPress development environment and apply patches for testing purposes. It’s outlined the process of cloning the WordPress repository, installing dependencies, building the project, and using Docker to create a working installation.

Moreover, details how to find suitable patches to test, apply them using different methods (for GitHub and regular patch files), and importantly, how to interact with the WordPress ticketing system by adding keywords to indicate issues like the patch needing refreshment or more information.

The discussion also covers the workflow for contributing to WordPress development through testing and reporting.

For the second section, we work on running and testing PHP unit tests within the WordPress system environment. We go through the process of setting up the environment using Docker and NPM commands, explaining how to execute both the full test suite and individual test groups or specific tests.

Then we do a demonstration reproducing a failing test, highlighting how to apply a patch to address the issue and re-run the tests to verify the fix, noting potential troubleshooting steps. Finally, we discuss on modifying existing unit tests to improve coverage and prevent future regressions, suggesting that testing and development often overlap.